1. Field of the Art
This invention relates to the field of power transmission devices utilizing meshing gear wheels which vary in size to provide differing ratios of power transmission. More specifically, the subject invention pertains to a transmission system wherein a driving gear is adjusted to contact differing transmission gears for the purpose of transfer of torque from an engine to a load, such as an axle or wheel.
2. Prior Art
Transmission devices for converting torque output of an engine to a variety of rotational speeds and variable driving forces are well-known in the art. In virtually every case, the object of such transmission devices is to transfer the torque developed in a drive gear which turns at the speed of rotation of a motor shaft, to a second shaft which is coupled to a load such as an axle, wheel, rotary bin, or other similar devices requiring torque to drive their movement.
The automobile transmission is perhaps the most common device requiring an adjustment of power from engine output to conform to the needs of a load such as an axle to drive the wheels of a vehicle. In a standard transmission arrangement, a gear box is used with meshing gear wheels for transferring torque output of the engine to the load. As is well-known, the transmission ratio (or gear ratio) is dependent upon the ratio of the numbers of teeth of the meshing gear wheels. These respective gear wheels are typically referred to as the driving gear (which runs at engine speed) and one or more transmission gears, which are housed on a separate shaft, referred to as the lay-shaft or transmission drive shaft. In a typical gear box, the driving shaft and lay-shaft are parallel in orientation and serve as a mount for the respective drive and transmission gears. Because of the differences in size of gears required to develop variable transmission ratios for providing low to high-power gear ratios, such gears must be displaced at various distances along the respective drive and lay-shafts.
This is illustrated, for example, in FIG. 1 which shows a conventional gear box arrangement. In this representation, the respective numerals 10, 11, and 12 represent differing gear ratios utilized to vary the torque applied to the lay or transmission drive shaft 15. For example, it is readily noted that when gears 10a and b are meshed, gear combinations 11 and 12 are not aligned. Likewise, the remaining gears of different size on the drive shaft 14 are in non-alignment with corresponding gears on the transmission drive shaft 15.
With this prior art embodiment, it is clear that multiple drive gears 10a, 11a, and 12a are required to obtain variable transmission ratios for torque transfer to the respective transmission gears 10b, 11b, and 12b. The use of multiple drive gears of different sizes results in complexity of movement control to maintain non-working gears out of mesh while the single working gear pair (i.e., 12a and 12b) are in meshing contact. Furthermore, this arrangement requires a larger gear box in order to house all of the required gears and leads to many difficulties with respect to shifting gears with smooth and even power transmission at variable speeds.
Several transmission devices have developed from the basic gear box concept. In a synchromesh gear box, for example, all drive and transmission gears remain in constant mesh. Various transmission ratios are obtained by means of sleeves which are slid into drive position. In this arrangement, the teeth of the respective drive and transmission gears are helical or spiral in geometrical configuration. This arrangement requires greater complexity and increased expense in order to obtain variable transmission effects. The primary distinction between the synchromesh gear box and the conventional gear box represented by FIG. 1 is that the former gear wheels are brought into mesh by sliding only when the actual gear change is performed. This is in contrast to the constant mesh of the synchromesh system. Based on this distinction, the subject invention relates to conventional gear box systems as opposed to synchromesh concepts.
Other forms of transmission systems exist within the prior art and share the common objective of developing changes in applied torque from the output of an engine or prime mover. To this extent, the transmission of the subject invention is designed to have similar utility. A comparison of mechanical approaches to this objective, however, may well place many of the mechanical transmission systems (such as the synchromesh) outside the actual field of the invention which relates most closely to the conventional gear box shown in FIG. 1.
Based on an overview of transmission systems in general, each state of the art system has one or more of the following problems or defects. The apparatus may be large and bulky in view of multiple gear requirements on the drive shaft and mechanical components necessary to provide control and smooth transition between contacting gears and gear reductions. Many transmission systems do not provide constant gear mesh and therefore increase the difficulty of changing gears without damage, manipulation of engine or vehicle speed, etc. Other transmission devices rely on systems of belt drive to obtain variable power output. Such belt systems require frequent adjustment and have limitations as to speed and power ratings. An additional problem with many conventional transmission devices is the limitation that power input must be on a specific input shaft as opposed to being reversible with the power output side.